Those skilled in the art will appreciate the manner in which intake and exhaust valves are employed in cylinder heads of internal combustion engines. Such valves, supported for reciprocal motion within valve guides, typically include integral elongated stems extending away from the engine cylinder heads, the ends of the stems interacting with rotating overhead cams for cyclic or repeated opening and closure of the valves against the force of valve return springs during the combustion cycle. Obviously, in order to permit unobstructed reciprocal movement of the stem in the guide, some mechanical clearance must exist between the valve guide and the moving stem. A plurality of valve stems thus move reciprocally to and from the cylinder head, each within its individual guide, and so-called valve stem seal assemblies are used to seal against leakage of oil through a mechanical clearance path between each annular engine valve guide and its associated valve stem.
In the typical engine, a valve stem seal assembly is fitted over or atop each valve guide, wherein each seal assembly includes a retainer frictionally mounted to an associated valve guide. Each valve stem seal assembly normally has two primary parts: 1) an elastomeric oil seal for controlling leakage of oil between the valve stem and guide as noted, and 2) a structural cylindrical retainer mounted atop of the valve guide to hold the oil seal in place.
Much progress has been achieved in valve stem seal design, performance, and construction. In some instances, there is a horizontal limit that constrains when or if typical seal designs can be made. In the molding process, the mold needs vertical access to a metal retainer surface to “shut-off” the rubber flow. In some designs it is desired to have a lower metal diameter smaller than this would normally allow. This usually applies when valve guides are thin, providing little room for rubber. Adapting seal designs to accommodate the diameter limitations would result in a more costly valve stem seal assembly. In view of the described limitations it would be desirable to have a formable metal retainer that could eliminate size limitations of current seal designs, while also reducing the costs to manufacture a valve stem seal assembly to meet these specifications.